The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Failures in Fixed Partial Denture
(Prosthodontics FPD- Dental science)
Various types of failures in the fabrication of fixed partial denture
Dr.Sachin Sunny Otta
St.Gregorios Dental College,Kothamangalam,Ernakulam
One of the best seminar of the author. Covered in detail regarding the increasing vertical dimension, centric relation, methods to record centric relation, philosophies of occlusion and in detail everything about full mouth rehabilitation.
Failures in Fixed Partial Denture
(Prosthodontics FPD- Dental science)
Various types of failures in the fabrication of fixed partial denture
Dr.Sachin Sunny Otta
St.Gregorios Dental College,Kothamangalam,Ernakulam
One of the best seminar of the author. Covered in detail regarding the increasing vertical dimension, centric relation, methods to record centric relation, philosophies of occlusion and in detail everything about full mouth rehabilitation.
Restoration of endodontically treated teeth 1 /certified fixed orthodontic c...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
Retainers in FIXED PARTIAL DENTURES(FPDS) AND RESIN BONDED FPDNAMITHA ANAND
DIFFERENT RETAINERS IN FPD ARE DISCUSSED WITH PICTURES AND REFERENCES AND SPECIAL CONSIDERATION FOR RESIN BONDED FPDS PARTIAL COVERAGE RESTORATIONS AND INTRACORONAL RESTORATIONS
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
This presentation provide brief information about different types of cements in Dentistry. also you will find information about cementation tips and techniques. Recent resin cements are also included in this presentation
Indian Dental Academy: will be one of the most relevant and exciting
training center with best faculty and flexible training programs
for dental professionals who wish to advance in their dental
practice,Offers certified courses in Dental
implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic
Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting
training center with best faculty and flexible training programs
for dental professionals who wish to advance in their dental
practice,Offers certified courses in Dental
implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic
Dentistry, Periodontics and General Dentistry.
Restoration of endodontically treated teeth 1 /certified fixed orthodontic c...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
Retainers in FIXED PARTIAL DENTURES(FPDS) AND RESIN BONDED FPDNAMITHA ANAND
DIFFERENT RETAINERS IN FPD ARE DISCUSSED WITH PICTURES AND REFERENCES AND SPECIAL CONSIDERATION FOR RESIN BONDED FPDS PARTIAL COVERAGE RESTORATIONS AND INTRACORONAL RESTORATIONS
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
This presentation provide brief information about different types of cements in Dentistry. also you will find information about cementation tips and techniques. Recent resin cements are also included in this presentation
Indian Dental Academy: will be one of the most relevant and exciting
training center with best faculty and flexible training programs
for dental professionals who wish to advance in their dental
practice,Offers certified courses in Dental
implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic
Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting
training center with best faculty and flexible training programs
for dental professionals who wish to advance in their dental
practice,Offers certified courses in Dental
implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic
Dentistry, Periodontics and General Dentistry.
When a crown or Fixed Partial Dentures (FPD) fails, the primary question is whether the problem can be easily resolved, or requires extensive rehabilitation and reconstruction.
Retention in fpd /certified fixed orthodontic courses by Indian dental academy Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
Retention in fpd /certified fixed orthodontic courses by Indian dental academy Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
The pediatric dentistry in the restorative to the damaged tooth by the caries and the prevention for the further shedding and erupting of the permanent tooth.
Finish lines/cosmetic dentistry course by Indian dental academyIndian dental academy
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
The presentation depicts in a very simplified manner the steps of cavity preparation and restoration of class 3 and class 5 composite restoration. It is well supported with illustrations that further provide a better understanding of the topic.
Finish lines/certified fixed orthodontic courses by Indian dental academy Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
Retention in fixed partial dentures / cosmetic dentistry courseIndian dental academy
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
Principles of tooth prep /certified fixed orthodontic courses by Indian denta...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
Copy of fundamentals of cavity preparations / dental implant coursesIndian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.
Opportunity for Dentists (BDS/MDS )to relocate to United kingdom -Register as a DENTAL HYGIENIST/ DENTAL THERAPIST without Board exams and after approval you can register in GDC as a DH/DT and start working as a DH/DT Immediately and get paid.
You can complete the whole process in 3-4 months.Salary range for DH/DT is around 2500-3500 Pounds per month.
Eligibility / requirements-
1. An International English Language Testing System (IELTS) certificate
at the appropriate level.(Within 2 yrs of application date )
2: A recent primary dental qualification that has been taught and examined in English..(Within 2 yrs of application date )
3: A recent pass in a language test for registration with a regulatory authority in a country where the first language is English.
If you are interested Please contact us for more details.
1ST, 2ND AND 3RD ORDER BENDS IN STANDARD EDGEWISE APPLIANCE SYSTEM /Fixed ort...Indian dental academy
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals
who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry,
Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
I –Aligners are made with FDA approved transparent thermoplastic materials using 3D scanning, 3D Printing and finally Trays with Pressure vacuum formers.
Dear Doctor,
Indian Dental Academy Now offers comprehensive online Orthodontics course.
Course includes:
1.whiteboard lecture presentations
2.Case Discussions
3.with hundreds of pictures.
4.Demo on Models
5.Demo on Patients
6. subtitles in your own language
12 months unlimited access and support @350 USD only.
For Demo please visit :www.idalectures.com/preview/
For more details visit: www.idalectures.com
Please contact us for any clarifications:
idalectures@gmail.com
indiandentalacademy@gmail.com
Thanks & Regards
Indian Dental Academy
--
Indian Dental Academy
Leader in continuing dental education
www.indiandentalacademy.com
skype:indiandentalacademy
+919248678078
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Cytotoxicity of silicone materials used in maxillofacial prosthesis / dental ...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Diagnosis and treatment planning in completely endntulous arches/dental coursesIndian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Properties of Denture base materials /rotary endodontic coursesIndian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Use of modified tooth forms in complete denture occlusion / dental implant...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
2. INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.com
3. Fixed prosthodontic treatment can offer exceptional
satisfaction for both patient and dentist. It can transform an
unhealthy, unattractive dentition with poor function into a
comfortable, healthy occlusion capable of giving years of
further service while greatly enhancing esthetics. To achieve
such success, however, requires meticulous attention to every
detail from initial patient interview, through the active
treatment phase, to a planned schedule of follow-up care.
Failure to achieve the desired specifications of design for
function and esthetics would result in failure of the prosthesis.
www.indiandentalacademy.com
4. The causes of FPD failures were summarized as early as
in 1920 when Tinker wrote “ Chief among the causes for such disappointing results have
been:
First : Faulty, and in some cases, no attempt at diagnosis and
prognosis.
Second: Failure to remove foci of infection in attention to
treatment and care of the investing tissues and mouth
sanitation.
Third: Disregard for tooth form
Fourth: Absence of proper embrasures
Fifth: Inter-proximal spaces
Sixth: Faulty occlusion and articulation”
www.indiandentalacademy.com
6. Bennard G. N. Smith
1. Loss of retention
2. Mechanical failure of crowns or bridge components
a. Porcelain fracture
b. Failure of solder joints
c. Distortion
d. Occlusal wear and perforation
e. Lost facings
3. Changes in the abutment tooth
a. Periodontal disease
b. Problems with the pulp
c. Caries
d. Fracture of the prepared natural crown or root
e. Movement of the tooth
www.indiandentalacademy.com
7. 4. Design failures
a. Under-prescribed FPDs
b. Over-prescribed FPDs
4. Inadequate clinical or laboratory technique
a. Positive ledge
b. Negative ledge
c. Defect
d. Poor shape and color
4. Occlusal problems
www.indiandentalacademy.com
8. John F. Johnston
1. Discomfort
a. Malocclusion or premature contact
b. An oversized or poorly positioned mastication area, with
retention of food by pontics or retainers.
c. Torque produced from the seating of the bridge or from
occlusion
d. An excess of pressure on the tissue
e. Plus or minus contact area
f. Over protected or under protected gingival and ridge tissue.
g. Thermal shock
www.indiandentalacademy.com
9. 2. Looseness of FPD
a. Deformation of the metal casting on the abutment
b. Torque
c. Technique of cementation
d. Solubility of cement
e. Caries
f. Mobility of one or more abutments
g. Lack of full occlusal coverage
h. Insufficient retention in the abutment preparation
i. Poor initial fit of the casting.
www.indiandentalacademy.com
10. 3. Recurrence of caries
a. Over extension of margins
b. Short castings
c. Open margins
d. Wear
e. A retainer becoming loose
f. Pontic form that fills the embrasure
g. Poor oral hygiene
h. Use of wrong type of retainer, which will promote caries
susceptibility
i. Permanent displacement of the gingiva due to temporary
protection
www.indiandentalacademy.com
11. 4. Recession of supporting structure
a. Length of the span
b. Size of the occlusal table
c. Embrasure form
d. Few extensions of the cervical margins
e. Impression technique can also stimulate recession of the
gingiva.
4. Degeneration of Pulp
5.
Fractures of bridge components
a. A faulty solder joint
b. Incorrect casting technique
c. Overwork of the metal due to length of the span or parts
that are too small.
www.indiandentalacademy.com
12. 7. Loss of veneers
a. Little retention
b. Badly designed metal protection
c. Deformation of the protecting metal
d. Malocclusion
e. Improper fusing or technique
7. Loss of function
a. They don’t function in occlusion
b. They have no contact with opposing teeth
c. They have permanent contact
d. Over carved or under carved occlusal surface may impair
efficiency
e. Loss of opposing or approximating teeth
www.indiandentalacademy.com
13. 9. Loss of teeth tone or form
a. Pontic design
b. Position and size of the joints
c. Embrasure form
d. Over contouring or under contouring of retainers
e. Oral hygiene practiced by the patient
9. Failure to seat
a. The abutment preparations may not be near parallel
b. Soldering assembly may have been incorrect, or relationship
of the retainers may have been altered during soldering.
www.indiandentalacademy.com
14. TYPES OF BRIDGE FAILURE
I. Cementation failure
II. Mechanical failure
III. Gingival and periodontal breakdown
IV. Caries
V. Necrosis of pulp
VI. Biomechanical failure
VII.Esthetic failure
www.indiandentalacademy.com
16. Cementation failures can be broadly divided into:
1. CEMENT FAILURE
2. RETENTION FAILURE
3. OCCLUSAL PROBLEMS
4. DISTORTION OF FPD
www.indiandentalacademy.com
17. 1. CEMENT FAILURE
The primary function of the luting agent is to provide a
seal preventing marginal leakage and pulp irritation. The
luting agent should not be used to provide significant retentive
and resistive forces.
An ideal luting agent would have the following properties:
1. Adequate working time
2. Adhere well to both tooth structure and metal surface
3. Provides a good seal
4. Non toxic to the pulp
5. Have adequate strength properties
6. Be compressible into thin layers
7. Have low viscosity and solubility
8. Exhibit good working time and setting properties
www.indiandentalacademy.com
18. Besides an inadequate retainer, failure can also occur because of a
poor cementation technique. This maybe due to the wrong
choice of material, failure to observe the manufacturer’s mixing
instructions, the use of old or contaminated material, an
inadequate powder/liquid ratio, or the insertion of the
prosthesis when the cement has started to set.
An inadequately cemented restoration may cause
1. An increased vertical dimension of occlusion
2. A loosening of the crown or FPD after a relatively short time
3. Leakage and decay under the abutment
4. The unsightly appearance of a metal margin where originally
the metal was concealed under the gingiva
5. Sensitivity to sweets or brushing due to exposure of the cervical
end of the tooth
www.indiandentalacademy.com
19. Causes of cement failure
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Cement selection
Old cement
Prolonged mixing time
Thin mix
Cement setting prior to seating
Inadequate isolation
Incomplete removal of temporary cement
Thick cement space
Inclusion of cotton fibers
Insufficient pressure
www.indiandentalacademy.com
20. 2. RETENTION FAILURE
For a restoration to accomplish its purpose, it must stay in
place on the tooth. No cements that are compatible with living
tooth structure and the biologic environment of the oral cavity
possess adequate adhesive properties to hold a restoration in
place solely through adhesion. The geometric configuration of
the tooth preparation must place the cement in compression to
provide the necessary retention and resistance.
CAUSES FOR RETENTION FAILURE
1) Excessive taper
2) Short clinical crowns
3) Mis-fit
4) Misalignment
www.indiandentalacademy.com
21. Excessive taper : As a cast metal or ceramic restoration is placed
on or in the preparation after the restoration has been fabricated in
its final form, the axial walls of the preparation must taper slightly
to permit the restoration to seat
Theoretically, the more nearly parallel the opposing walls
of the preparation are, the greater should be the retention.
Recommendations for optimal axial wall taper of tooth
preparations for cast restorations ranged from 10 to 12 degrees.
Tooth preparation taper should be kept minimal because of
its adverse effect on retention, but Mock estimates that a minimum
taper of 12 degrees is necessary just to insure the absence of
undercuts.
www.indiandentalacademy.com
22. Short clinical crown : Cement creates a weak bond largely by
mechanical interlocks between the inner surface of the restoration
and the axial wall of the preparation. Therefore, the greater the
surface area of the preparation the greater is its retention. The
preparations on large teeth are more retentive than preparations on
small teeth.
A short, over-tapered or short clinical crown would be
without retention as there would be many paths of removal.
For the restoration to succeed, the length must be great
enough to interfere with the arc of the casting pivoting about a point
on the margin on the opposite side of the restoration. A shorter wall
cannot afford this resistance. The walls of short preparations should
have as little taper as possible.
www.indiandentalacademy.com
23. Clinical conditions with excessive taper and short clinical crowns
should be treated with :1. In case of excessive taper:
a. Incorporation of proximal grooves.
b. Additional retentive grooves (should be along with the path
of insertion).
c. Additional pins
2. In case of short crowns:
a. Crown lengthening procedure
b. Modification of supra-gingival margin to sub-gingival
margin
c. Additional retentive grooves and proximal box
d. Incorporation of pins
e. Addition of extra abutments
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24. Misfit : The fit of casting can be defined best in terms of the
“misfit” measured at various points between the casting surface
and the tooth.
The measurement of misfit at different locations and geometrically
related to each other and defined as :
1. Internal gap
2. Marginal gap
3. Vertical marginal discrepancy
4. Horizontal marginal discrepancy
5. Over-extended margin
6. Under-extended margin
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25. Causes for misfit :
a. Expansion of the metal substructure
b. Improper water / powder ratio
c. Improper mixing time
d. Improper burnout temperature
e. Distortion of the margins (towards the tooth surface)
f. Distortion of the metal substructure
g. Metal bubbles in occlusal or marginal regions
i. Inadequate vacuum during investing
ii. Improper brush technique
iii. No surfactant
h. Porcelain flowed inside the retainer
i. Excessive oxide layer formation in inner side of the retainer (due
to contaminated metal or repeated firing of porcelain)
j. Tight contact points
k. Thick cement space
l. Insufficient pressure during cementation procedure
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26. Misalignment : In case of the fixed FPD, it is more difficult to
differentiate whether a FPD is not seating because of a faulty fit,
or the alignment of the retainers relative to each other is incorrect.
The only difference which may sometimes be apparent is that, in
the case of misalignment the FPD will have some ‘spring’ in it and
tend to seat further on pressure due to the abutment teeth moving
slightly, whereas in the case of a defective fit, the resistance felt
will be solid.
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27. Causes for misalignment
a. Abutment displacement due to improper temporization.
b. Distortion of wax pattern while sprueing and investing.
c. Casting defects.
d. Distortion of metal frameworks in porcelain firing.
e. Porcelain flow inside the retainers.
f. Misalignment of soldering points.
g. Insufficient pressure in cementation.
h. Thick cement film.
i. Excessive metal or porcelain in tissue surface (ridge lap) of
pontic prevents the proper seating of FPD and open margin
(can be detected by observing the blanching of the tissue or
patient may complain of pressure on the pontic region).
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28. 3. OCCLUSAL PROBLEMS
Following the placement of a dental restoration, a patient
might report discomfort ranging from a feeling of ‘lameness’ to
‘severe and constant pain’. Sensitivity, in most cases, is due to
pulp irritation from traumatic contact or greater leverages. When
the occlusion has been adjusted, each type of discomfort may be
relieved almost instantly and should disappear shortly.
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29. Causes in occlusal problems
1. Immediate problems
Occlusal interference
Marginal ridges at different levels
Supra eruption of the opposing tooth
Parafunctional habits
2. Delayed problems
Wearing of occlusal surface
Loss of occlusal contacts
Perforation of occlusal surface due to
• Porcelain Vs resin
• Porcelain Vs gold
Food lodgment due to plunger cusp
Fracture of facing due to defective occlusal contact
Periodontal or gingival breakdown due to improper occlusal
contacts
Tenderness due to www.indiandentalacademy.com
food lodgment
30. 4. DISTORTION OF FPD
Margin Integrity
The completed restoration should go into place without
binding of its internal aspect against the occlusal surface or the
axial walls of the tooth preparation. In other words, the best
adaptation should be at the margins. If the indirect procedure is
handled properly, there should be no noticeable difference between
the fit of a restoration on the die and that in the mouth.
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31. Causes for failure in marginal integrity:
1) Bending of FPD (wax patterns and metal substructure)
• In waxing stage
• Removal from the die
• Spruing stage
• Investing stage (thick mix of investment distort or displace
the wax pattern)
1) Incomplete casting
• Wax patterns too thin
• Incomplete wax elimination
• Cold mold or melt
• Inadequate metal
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32. 3) Rough casting
• Improper finishing of wax pattern
• Excess surfactant
• Improper water powder ratio
• Excessive burnout temperature
• Improper devesting (direct hit on the metal framework)
3) Bending of long span FPDs
• Thin crown
• Soft metal
• Heat treatment not being done
• Porosity in the metal
• Distortion of the metal substructure during the porcelain
firing
• Contaminated metal
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33. Inadequate FPD design
Designing FPDs is difficult. It is neither a precise science nor a
creative art. It needs knowledge, experience and judgment, which
takes years to accumulate.
So it is not surprising that some designs of FPDs, even though
well intentioned and consciously executed, fail. A simple
classification of these failures is as; under-prescribed and overprescribed FPDs.
Under-prescribed FPDs – these include designs that are unstable or
have too few abutment teeth. E.g., a cantilever FPD carrying pontics
that cover too long a span or a fixed movable FPD where again the
span is too long or where abutment teeth with too little support has
been selected.
Another ‘under-design’ fault is to be too conservative in
selecting retainers. E.g., intra coronal inlays for fixed FPDs. With
these design faults, little can be done other than to remove the FPD
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and use another type of replacement.
34. Over-prescribed FPDs – cautious dentists will somewhere include
more abutment teeth than necessary, and fate usually dictates that it is
the unnecessary retainer that causes fault. Some use the upper canines
and both premolars on each side in replacing the four incisor teeth. As
well as being destructive, this gives rise to unnecessary practical
difficulties in making the FPD. This, in turn, reduces the chance of the
FPD being successful.
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35. Several suggestions have been proposed scientifically to explain the
distortion resulting in metal frameworks after the various stages
of the porcelain firing schedule; these include:
a)
b)
c)
d)
e)
f)
g)
h)
Contraction of the porcelain with subsequent metal deformation
Contamination of the casting, reducing its melting temperature
Grain growth of the alloy, constricting the diameter of the crown
Plastic flow and creep of the porcelain gold alloy at high
temperatures
Reduction in the resiliency of the metal due to the rigidity of
porcelain
Improper support of the framework during firing
Inadequate framework design at the gingival level
inadequate design of the framework as a whole
Shillingburg stated that ceramic metals require a certain amount
of
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bulk in the cervical area to resist distortion when subjected to the
37. In the design of fixed partial denture pontics, if insufficient
attention is given to mechanical principle, the prognosis will be
compromised. Mechanical problems might be due to poor diagnosis
and treatment plan, improper choice of materials, poor framework
design, poor tooth preparation, or poor occlusion. These could lead
to fracture of the prosthesis or displacement of the retainers.
It is therefore important to evaluate the likely forces on a
pontic and to design it accordingly. For example, a strong all metal
pontic may be needed in situations of high stress rather than a metal
ceramic pontic which could be more susceptible to fracture.
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40. 1) Perforation
Causes
a) Insufficient occlusal reduction
b) Insufficient occlusal material
c) High points in opposing dentition (plunger cusp)
d) Premature contacts
e) Contaminated metal
f) Porosity in metal work (subsurface, back pressure, suck
back)
g) Due to improper melting temperature
h) Improper pattern position
i) Improper sprue (too thin)
j) Improper location
k) Parafunctional habits
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41. 2) Marginal discrepancy
Causes
a) Selection of margin
b) Improper preparation and failure to establish the margin
properly
c) Failure to do gingival retraction prevents definite margin
location and subsequently in impression
d) Selection of the impression material
i. Shrinkage in material (condensation silicon)
ii. Distortion of material (alginate)
e) Improper impression procedures
f) Voids in the impression
g) Variation in pressure application in wash technique
h) Delayed pouring of die material
i) Distortion of wax patterns at margins
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42. j)
Insufficient flow of metal
k) Shrinkage of metal
l) Nodules in margins and inner side of coping
i. Due to inadequate vacuum during investing
ii. Improper brushing technique
iii. No surfactant
l) Excessive sand blasting
m) Distortion due to degassing procedure
n) Open margins due to porcelain shrinkage (opaque porcelain)
o) Thick cement
p) Cement setting prior to seating
q) Insufficient pressure application during cementation
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43. 3. Facing failure
Types of veneer failures
a) Fracture
b) Wearing of facing (resin veneers)
c) Discoloration
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44. Causes for veneer fracture:
i. Too little retention (mechanical)
ii. Badly designed metal protection
iii. Deformation of the protecting metal
iv. Malocclusion
v. Micro-leakage between metal and facing
vi. Improper curing or fusing technique
vii.Excessive oxide layer formation
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45. Cause of wearing of facing:
i.
ii.
iii.
iv.
v.
Improper curing or fusing technique
Deep bite (decreased overbite in lower anteriors)
Acrylic veneering opposing porcelain teeth
Faulty brushing techniques and flossing
Parafunctional habits
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46. Causes of discoloration:
i. Absorption of oral fluids
ii. Absorption of artificial food colouring agents through
micro-cracks or microleakage in metal and facing
interfaces
iii. Tarnish of underlying metal and facing (greening of
porcelain in silver alloys)
iv. Micro-cracks due to malocclusion
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47. 2. PONTIC FAILURE
Factors affecting selection and failure of pontics
1) Pontic space
2) Residual ridge contour
3) Biological consideration
a. Ridge relation
b. Dental plaque
c. Gingival surface of pontic (Contact with mucosa)
i. Mucosal contact
ii. Non mucosal contact
4) Pontic ridge relationship
5) Pontic material
6) Biocompatibility
7) Occlusal forces
8) Metal substructure support
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48. 1) Pontic space
One function of an FPD is to prevent tilting or drifting of
the adjacent teeth into the edentulous space. If such unwanted
movement has already occurred the space available for the
pontic may be reduced and its fabrication may be complicated.
Under these circumstances it is often impossible to create an
acceptable appearance without repositioning the abutment
teeth orthodontically where aesthetics is important.
Even with a less aesthetic requirement, as for posterior
teeth, overly small pontics are unacceptable because they trap
food and are difficult to clean. When orthodontic repositioning
is not possible, it may be better to increase the proximal
contours of adjacent teeth than to make an FPD with
undersized pontics.
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49. 2) Residual ridge contour
The contour texture of the edentulous ridge should be
carefully evaluated during the treatment planning phase. An ideally
shaped ridge will be smooth, for this is the easiest to maintain
plaque free. Unfortunately, many patients present with irregular
hypoplastic tissue, particularly where an ill fitting RPD has been in
place, and under these circumstances , surgical removal of the
excess fibrous tissue may be recommended.
Some patients suffer severe bone resorption following tooth
loss, particularly if the loss occurred due to trauma. These patients
can present a significant aesthetic challenge. Surgical ridge
augmentation (e.g., with hydroxyl apatite) may be one solution.
Another surgical procedure that has been proposed is to create a
role of soft tissue labial to the pontic site, which will enhance the
illusion that a tooth is growing out of the gingival tissue.
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50. 3) Biological consideration
The biologic principles of pontic design pertain to the
maintenance and preservation of the residual ridge, abutment
and opposing teeth and supporting tissues.
Factors of specific influence are:
a) Pontic ridge contact
b) Removal of dental plaque
c) Gingival surface of the pontic
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51. a)Pontic ridge contact
Pressure free contact between the pontic and the underlying
tissues is indicated to prevent ulceration and inflammation of the soft
tissues. If any blanching of the soft tissue is observed at try in, the
pressure areas should be identified with pressure indicating paste and
the pontic re-contoured until tissue contact is entirely passive.
b)Dental plaque
The chief cause of ridge irritation is the toxins that are released
from microbial plaque, which accumulates between the gingival
surface of the pontic and the residual ridge causing tissue
inflammation and calculus formation.
Unlike a RPD, a FPD cannot be taken out of the mouth daily
for cleaning. To enhance plaque control, the patient must be taught to
perform efficient oral hygiene techniques, with particular emphasis
on cleaning the gingival surface of the pontic. The shape of the
gingival surface, its relation to the ridge, and the materials used in its
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fabrication will influence the success of these measures.
52. c) Gingival surface of the pontic
Where aesthetics is of concern in the anterior region of the
mouth, the pontic should contact the gingival tissue on the labial
or buccal aspect to give an appearance of ‘emerging from the
tissue’. In the posterior region, like the mandibular premolar and
molar areas more attention should be given to occlusion, function
and hygiene. Considering these aspects, pontic contacts may be
classified into different groups: mucosal and non mucosal contacts
based on the shape of the gingival surface and its relationship with
the underlying tissue.
Normally, where tissue contact occurs, the gingival surface
of a pontic is inaccessible for cleaning with a tooth brush.
Therefore, the patient must develop excellent hygiene habits and
the use of devices such as proxibrushes, pipe cleaners and dental
floss.
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53. A pontic with a concave fitting surface that overlaps the
residual ridge bucally and lingually is called a saddle. This is
avoided because the gingival surface cannot be easily cleaned.
An egg shaped or bullet shaped pontic is probably easiest
for the patient to keep clean. It should be made as convex as
possible, with only one point of contact at the center of the residual
ridge. This design is recommended for the replacement of
mandibular posterior teeth because aesthetics is of less concern
here.
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54. 4) Pontic ridge relationship
Since 1918 it has been a popular concept that the tissue
surface of a mandibular posterior pontic should sometimes be left
well clear of the residual ridge. This design was often called
‘hygienic’ or ‘sanitary’.
The hygienic design permits easier plaque control by
allowing gauze strips and other cleaning devices to be passed
under the pontic and seesawed in shoeshine fashion. There are
disadvantages to the design as well. Food particles tend to
become trapped, which may lead to tongue habits that are
annoying to the patient. The hygienic design also is
contraindicated if minimum vertical space exists and where
esthetics is important; tissue proliferation can occur when the
pontic is too close to the residual ridge, forgoing the originally
intended advantages.
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55. 5) Pontic material
Any material chosen to fabricate the pontic should provide
good aesthetic results where needed, biocompatibility, rigidity and
strength to withstand occlusal forces, and the desired longevity.
FPDs, during mastication or parafunction, may impinge upon the
gingiva and also the veneering material may fracture. In the
fabrication of metal-ceramic FPDs, the porcelain on the occlusal
surfaces should be carefully evaluation. Porcelain is a brittle
material and may fracture easily.
When a metal-ceramic restoration is chosen, it is of
paramount importance to design the metal substructure properly if
flexure and porcelain fracture is to be avoided. Occlusal contacts
should not fall on the junction between metal and porcelain during
centric and eccentric contacts.
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56. 6) Biocompatibility
Glazed porcelain is generally considered to be the most
biocompatible of the available pontic materials and clinical data
tends to support this opinion, although the critical factor seems
to be the material’s ability to resist accumulation of plaque
rather than the material itself. Highly glazed porcelain is
relatively easy to clean, making plaque removal from it easier
than from other materials. For ease of plaque removal, it is
recommended that the tissue surface of the pontic be made in
glazed porcelain whenever possible.
Well-polished gold is smoother, less prone to corrosion, and
less retentive of plaque than an unpolished or porous casting.
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57. 7) Occlusal forces
Reducing the buccolingual width of the pontic by as much
as 30% has long been suggested as a means of lessening occlusal
forces on abutment teeth. Narrowing the occlusal table may
actually impede or even preclude the development of a
harmonious and stable occlusal relationship. Like a malposed
tooth, it may cause difficulties in plaque control as well as fail to
provide proper cheek support. For these reasons, pontics with
normal occlusal widths are generally recommended.
Mechanical failure of the pontic may occur because of
inadequate strength. Thus an all-porcelain occlusal pontic should
never be used unless the bite is favourable.
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58. 8) Compromised metallic substructure
Causes
a. Limited edentulous space occluso-cervically due to supraeruption of opposing tooth.
b. Limited space mesiodistally due to migration or drifting of
adjacent tooth.
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59. How to avoid:
a. The framework must provide a uniform veneer of porcelain
(approx 1.2mm). excessive thickness of porcelain contributes to
inadequate support and predisposes to eventual fracture. This is
often true in the cervical portion of an anterior pontic. A reliable
technique for ensuring uniform thickness of porcelain is to wax
the fixed prosthesis to complete anatomic contour and then
accurately cut back the wax to a pre-determined depth.
b. The metal surfaces to be veneered must be smooth and free of
pits. Surface irregularities will cause incomplete wetting by the
porcelain slurry, leading to voids at the porcelain metal interface
that reduces bond strength and increases the possibility of
mechanical failure.
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60. c. Sharp angles on the veneering surface should be rounded.
They produce increased stress concentrations that could cause
mechanical failure.
d. The location and design of external metal porcelain junctions
need particular attention. Any deformation of the framework at
the junction can lead to chipping of the porcelain. For this
reason occlusal centric contacts must be placed at least 1.5mm
away from the junctions. Attention must be paid to excursive
eccentric contacts that might deform the metal ceramic
interface.
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61. 3. CONNECTOR FAILURE
The connector is that part of the FPD or splint that joins the
individual components (retainers and pontics) together.
Requirements of solders are their ability to resist tarnish and
corrosion, to be free flowing, to match the colour of the units to be
joined and to be strong. These factors also depend on the chemical
composition of the solder.
Casting can make a rigid connection as part of a multi unit
wax pattern or by soldering which involves the use of an
intermediate metal whose melting temperature is lower than that of
the parent metal. The parts being joined are not melted during
soldering, but they must be thoroughly wettable by liquefied solder.
Dirt or surface oxide can reduce wetting and impede successful
soldering.
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62. Causes for connector failure
a. Improper selection of connector
b. Thin metal at the connector
c. Incorrect selection of solder
d. Solder gap – narrow or wide
e. Porosity
f. Insufficient metal around
g. Defective occlusal contacts over thin connectors
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64. Margins are one of the most important and weakest links in
the success of FPD restorations. One of the prime goals of
restorative therapy is to establish a physiologic periodontal health.
A successful prosthesis depends on a healthy periodontal
environment and periodontal health depends on the continued
integrity of the prosthodontic restoration.
All displacement techniques have the potential damage
gingiva, attachment apparatus and bone, especially if anatomic
forms are weak or if disease is present.
In healthy patients, properly used cord displacement or
copper band methods have proved to be atraumatic.
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65. The margin is one of the components of the cast restoration
most susceptible to failure, both biologically and mechanically.
Most of the investigative proof shows that supragingival margins
are kinder to the gingiva than are subgingival margins. However,
practicality dictates that supragingival margins are not always
usable
There are three locations in which to prepare crown margins:
Supragingival
At the crest of the gingiva
Subgingival
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66. SUPRAGINGIVAL Vs SUBGINGIVAL MARGINS:
Whenever possible, the margin of the preparation should be
supragingival. Subgingival margins of cemented restorations have
been identified as a major factor in periodontal diseases, particularly
where they encroach on the epithelial attachment. Supragingival
margins are easier to prepare accurately without trauma of the soft
tissues. They can usually also be situated on hard enamel, whereas
subgingival margins are often on dentin or cementum.
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67. SUPRAGINGIVAL MARGINS
ADVANTAGES:
They can be easily finished
They are more easily cleaned
Impressions are more easily made, with less potential for soft
tissue damage
Restorations can be easily evaluated at recall appointments
DISADVANTAGE:
Aesthetically not indicated for anterior region
Metal can be seen
Not indicated in short clinical crowns
The proximal contacts extend to the gingival crest
In case of root sensitivity
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68. SUBGINGIVAL MARGINS
SPECIFIC DEMANDS FOR SUBGINGIVAL MARGINS:
Aesthetic demands
Caries removal
To cover existing subgingival restorations
To gain needed crown length
To provide more favourable crown contour
DISADVANTAGES:
Difficult for preparation
Gingival management should be perfect
Prone for soft tissue trauma
More prone for gingival and periodontal pathosis
Difficult to maintain oral hygiene
Metal margins can be seen thru the gingiva
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69. SOFT TISSUE PORBLEMS: GENERALIZED (Not due to bridge)
LOCALISED (May be due to
bridge)
Causes for soft tissue problems:
Over / under contouring
Narrow embrasures
Over / under extended crowns
Pressure of pontic over tissue
Loss of contact
Horizontal food impaction due to plunger cusp in the opposing
arch
Marginal ridges at different levels
Wide occlusal table
Trauma from occlusion
Parafunctional habits
Acrylic facing in contact with gingiva
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70. RESULTS OF IMPROPER CONTACT AREAS
Cause displacement of teeth bucally, lingually, mesially and
distally.
Exert a lifting force on the tooth when placed too high occlusally.
Disturb the axial relation of the teeth, resulting in trauma.
Cause rotation of the teeth.
Cause injury to the investing structures by excessively opening or
closing the contact and interproximal embrasures.
Disturb the coordination of the inclined planes and cusps causing
deflective occlusal contacts.
Cause vertical or horizontal food impaction.
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71. OVER EXTENDED CROWN
The over extended crown usually encroaches beyond the cut
of the preparation on the tooth and the excess beyond the margin of
the preparation is usually not in contact with the tooth surface. This
overhang impinges the gingival tissue, irritates and often causes
edema and proliferation of the gingival tissue, destruction of the
marginal alveolar bone and ultimate loss of the tooth. The overextension of the crown is usually due to inaccurate technique and /
or the dentists desire to ‘play safe’ by making it long enough to
cover the preparation or to extend beneath the gingival margin.
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72. SHORT CROWN
The short crown fails to cover the cut surface of the prepared
tooth and often does not extend below the gingival margin. This
uncovered ground tooth surface is often sensitive to sweets and to
temperature changes and invites development of caries and causes
gingival irritation. Also, it is usually due to inadequate technique
and a willingness of the dentist to accept impressions that are
incomplete.
CONTOUR
The poorly contoured crown is one which may have an
excess contour that impinges on the gingival tissue and deflects food
over and away from this tissue, thereby depriving it of its normal
stimulation; or it may be under contoured and permit the impaction
of food into the gingival crevice, thereby stripping the gingival
tissue away from the tooth. Either will cause irritation of the
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surrounding tissue and may lead to the loss of the tooth.
74. CAUSES
Iatrogenic (dentists role)
Failure to identify caries
Incomplete removal of caries
Rough abutment finishing margins
Subgingival marginal placement in inaccessible areas or regions
Burning of root dentin or cementum in electro surgical technique
(leads to damage or rough surface and causes plaque retention)
Overhanging margins
Rough margins of crowns or bridges
Over contouring of the cervical thirds of crowns or bridges
prevents the physiologic too cleaning by tongue or muscles
Marginal discrepancy
Thick cement space in margins leads to cement dissolution.
Narrow embrasures (inaccessibility to maintain hygiene)
Wide connector
Failure to motivate or educate the patient about oral hygiene
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75. Patient role
Systemic factors
Xerostomia
Due to radiation therapy
Drug induced
Endocrine disorders
Epilepsy (difficult to maintain the oral hygiene)
Rheumatoid arthritis
Local factors
Improper brushing and flossing
Dietary habits
Failure to understand importance of oral hygiene.
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77. Supporting structures or root length may be lost owing to
periapical involvement brought about by the method of preparation, lack
of protection of the prepared abutment teeth during construction, hidden
caries, and malocclusion. The preparation of the abutment tooth and the
building of the FPD, irritation from temporary coverage, lack of
temporary coverage, or malocclusion can activate a latent, low grade pulp
infection. There is no method of discovering such pulp conditions and
discomfort or pulp degeneration may occur due to such infections.
A pulp may degenerate because of too rapid preparation of the
tooth or because of improper cooling during preparation. Teeth
unprotected during the construction of a FPD are exposed to saliva and the
resulting irritation.
Pulp reactions to various procedures
Each step in full crown preparation presents hazards, which may
injure the pulp. The result may be pulpitis or even necrosis. Among the
many essential procedures that may cause pulp injury are tooth
preparation, impression making, temporization and cementation. In
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general, heat desiccation and / or chemical injury cause the insult.
79. Every restoration must be able to withstand the constant
occlusal forces to which it is subjected. This is of particular
significance when designing and fabricating an FPD, since the forces
that would normally be absorbed by the missing tooth are transmitted
through the pontic, connectors and retainers to the abutment teeth.
The abutment teeth are therefore called upon to withstand forces
directly to the missing teeth in addition to those usually applied to
them.
In addition to increased load placed on the periodontal
ligament by a long span FPD, longer spans are less rigid. Bending or
deflection varies directly with the cube of the length and inversely
with the cube of the occluso-gingival height of the pontic. Compared
with the FPD having a single tooth span, a two-toothed pontic span
will bend eight times as much, and a three-toothed pontic will bend
27 times as much.
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80. Owing to the fact that forces are being applied though the
pontics to the abutment teeth, the forces on the castings serving as
retainers are different in magnitude and direction from those
applied to a single restoration. The dislodging forces on an FPD
retainer tend to act in a mesio-distal direction as opposed to the
common bucco-lingual direction of forces on single restorations.
Preparations should be modified accordingly to produce greater
resistance and structural durability e.g. grooves on buccal and
lingual surfaces. Double abutments are sometimes used as a means
of overcoming problems created by unfavourable crown-root ratios
and long spans. A secondary abutment must have at least as much
root area and as favourable a crown-root ratio as the primary
abutment it is intended to bolster.
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82. REASONS FOR ESTHETIC FAILURE
Failure to identify patient expectations regarding esthetics
Improper shade selection
Excessive metal thickness at incisal and cervical regions
Thick opaque layer application
Surface blistering (chalky appearance)
Over glazing or too smooth a surface
Metal exposure in connector, cervical and incisal regions
Dark space in cervical third due to improper pontic selection
(anteriors)
Failure to produce incisal and proximal translucency
Improper contouring
Failure to harmonize contra lateral tooth morphology
Contour
Color
Position
Angulation
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Discoloration of facing
84. Failures in FPD construction for the most part is due to
attempted short cuts or positive indifference and inexcusable
ignorance on the part of those concerned with building the
prosthesis. Also a FPD can just wear out and this cannot be called
as failure and no lifetime guarantee can be given.
Failures most often occur because of violation of principles
either collectively or individually. This may be due to reactions of
the soft tissue and reactions of the abutment.
It is better to speak of the level of acceptability to the
patient and the dentist and consider what needs to be done to
improve the treatment. The fundamentals of fixed prosthodontic
therapy modality have to be followed strictly, failure of which will
lead to the failure of the prosthesis itself.
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86. 1. I. Gerson (1957) – stated that inadequately cemented
restorations may cause an increased vertical dimension,
loosening of the crown or FPD after a relatively short time,
microleakage and decay under the abutments, exposure of metal
margins and sensitivity.
2. Kenneth C. Pruden (1957) – stated that the multiple abutments
should be resorted to only where the added support or root
length is needed, and only periodontally sound teeth should be
included.
3. Leonard I. Linkow (1962) – gave the importance of form, type,
shape and position of contact areas. He stated that the contacts
which are flat, open, improperly placed, rough, or poorly
polished will lead to displacement of teeth and exert a lifting
force, disturb, the axial relationship, injure supporting tissues,
produce a deflective occlusal contact and vertical or horizontal
food impaction.
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87. 4. Marvin Reynolds (1964) – reviewed the properties of porcelain,
acrylic resin and gold as related to their use in pontics. He stated
that acrylic resin does not permit the precise control of color and
light refraction as it absorbs oral fluids and is less resistant to wear
and abrasion. Gold alloys provide the best strength to withstand the
stresses of occlusion and resistance to wear. Porcelain is superior to
other materials as it maintains the color, is resistant to abrasion and
is dimensionally stable and insoluble to oral fluids.
5. Richter et al (1970) – studied the tensile strength and compressive
strength of cements. The results showed the tensile strength of zinc
phosphate, hydrophosphate and ZnOE cements are equal,
carboxylate cements had less strength properties. Compressive
strength is lowest with carboxylate and highest with zinc phosphate.
6. Guy M Newcomb (1974) – investigated the location of subgingival
margins and related that to gingival inflammation. The results
showed that the least inflammation is observed when subgingival
crown margins are placed at the gingival crest or just into the
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gingival crevice.
88. 7. Brule et al (1981) – conducted a study on placement of margins in
anterior veneer crowns. He concluded that the subgingival margin
placement of anterior crown for esthetics might be unnecessary
except in some cases like in short clinical crowns.
8. Abraham Revah et al (1985) – discussed the problems with tilted
posterior tooth in relation with path of insertion. He advised the
mesial half of the crown be with parallel seating grooves for better
seating and retention.
9. Aaron H Wilson et al (1994) – examined the relationship between
degree of convergence or a machined metal die and retention of its
casting. The retention was found to increase from 0 degree
convergence to a peak between 6 -12 degree convergences.
Convergence angles of less than 6 degrees are not advisable as it
causes incomplete seating of the crown due to increase in
hydraulic pressure in between the crown and cement.
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89. 10. Paulo Baldissara et al (1998) – conducted a comparative
study about the marginal microleakage of six cements in
fixed provisional crowns. Results showed Zinc phosphate
and cavity bas compound cements had the best sealing
properties than other cements.
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